In integrated circuits (ICs), various devices such as transistors, resistors, inductors, capacitors and varactors are configured to achieve the desired function. During fabrication of these devices, trenches are formed to provide electrical connections for devices or to isolate devices such that they operate independently without interfering with each other.
Nevertheless, materials at the edge of a wafer used for forming the ICs are undesirably removed during processing of the trenches. These materials will redistribute across the surface of the wafer, causing contamination. This will result in severe defects and yield loss.
From the foregoing discussion, it is desirable to provide a method which effectively prevents contamination of wafer, thereby avoiding defects in the ICs.